1. Field of the Invention
This invention relates to valve and valve actuators, and more particularly it relates to a multiinput control shuttle valve assembly readily arranged for any desired number of separate inputs in its controlling function.
2. Description of Prior Art
In oil field practices, it is conventional to employ shuttle valves for the remote controlling of fluid actuated drilling and production devices, such as blowout preventer stacks. The conventional shuttle valve is a three port device having two inputs and one output, wherein each input is exclusive in function of the other input. These shuttle valves are relatively efficient when it is necessary to control a fluid actuated unit such as a blowout preventer stack from only two inputs fluid signals. However, it is now a requirement that certain blowout preventer stack be also adapted for actuation by acoustic control mechanisms. For example, the blowout preventer stacks must be adapted for operation with acoustic control systems so that if the conventional inputs from the surface to the shuttle valve are interrupted, an acoustic generator can be dropped adjacent the wellhead and the acoustic sensing valve supplied by a hydraulic accummulator applies hydraulic pressure to one input of the shuttle valve for operating the blowout preventor stack as now required by federal regulations.
It will be apparent that with the conventional shuttle valve with only two inputs the acoustic control regulations cannot be directly met since there is no additional input for the acoustic control system. Attempts have been made to comply with the acoustic control regulations, through the ganging of the conventional dual input shuttle valves. However, this situation has led to complex piping systems which in and of themselves lead to additional non-failsafe problems with blowout preventer arrangements such as employed on sea floor well templates.
The present invention is a shuttle valve to solve the multiinput requirements of drilling and production units such as blowout preventer stacks, where the shuttle valve arrangement can be adapted to accommodate any desired number of inputs in a convenient manufacturing and construction practice.